Tin, I have been beavering away with research too. I think I will go the DIY way if it becomes reality as the fun for me might be in making the machine! The Ordbot Hadron is a very interesting open source design that is high quality. This is just the frame and steppers and will be cheaper on your side of the world.
http://www.robotronics.com.au/web/products/ord-bot-hadron-mechanical-platform
It is made of Makerslide which is a cool open source extrusion that is designed for making 3D printers. There are a lot of accessories available to bolt it all together. 3D drawings are available.
Feedback from guys with CNC and cheap printers is getting the Z axis working well with two steppers is problematic as the steppers can get out of sync. So If I build one, it will be no holes barred.
So my current thinking For the Z is to use linear slides to move the bed up and down and a single 1202 Ball slide (12mm shaft, 2mm pitch) driven by a 400 step (0.9deg) stepper. This will give 5 micron accuracy without microstepping. If the ball screw is centred on one side of the build platform, a couple of rods and linear bearings might be added on the opposite two corners.
I thought the X axis would be attached to the Z axis platform and the Y axis suspended from above.
I was trying to avoid using belts as keeping them tight to eliminate backlash is problematic but it seems that ball screws are a bit to slow on the X & Y axes. The other fast technology is to use a gear rack on the axis with a cog on the stepper as per the longitudinal drive on a lathe. I just don't know how much backlash this might add to the system or how to control it.
The RUMBA board supports up to three extruders and the configuration shown has a newer stepper board that runs cooler (which I know is problematic from playing with the 4988 driver board)
http://www.robotronics.com.au/web/products/rumba-3d-printer-controller-drv8825
I was gong to use the opensource Bulldog XL extruder using a bowden setup that moves the heavy stepper assembly off the moving platform for speed (eg Bowden cable is like the throttle cable on a lawn mower)
http://www.robotronics.com.au/web/products/bulldog-extruder-xl
Once configured with the hot ends, this extruder path is quite pricey at around $250 each and I was up for around $1k for a single extruder model with roughly a 12" (305mm) cube as a build area.
Because I have a relationship with a laser cutter, I thought the frame would be cut from 2mm or 3mm steel plate. This would allow precise positioning of mounting holes plus add a bit of weight which has to help accuracy.
Hope that helps (or confuses)